The overarching goal is to better understand auditory processes underlying perception of speech and other complex sounds. One current goal is to continue development of signal processing algorithms for spectral enhancement. The focus is upon improvement of speech recognition in the face of extreme context-sensitivity resulting from co articulation. This effort is directed toward incorporation in facilitative devices such as hearing aids. The algorithm, currently successful with normal hearing listeners with simulated hearing loss, will be further improved, and testing will be extended to a population of listeners with hearing impairment. [unreadable] [unreadable] The second major goal is to describe and model processes by which the auditory system maintains perceptual constancy despite variations commonly encountered across sound sources (such as different talkers) and across different sound environments. More specifically, reveal auditory mechanisms that serve to compensate for reliable spectral and temporal characteristics of a sound source and of the ambient environment more generally. The primary focus is to further understand perception of speech, and the manner in which these auditory processes explain how listeners understand speech across variations in characteristics of individual talkers, as well as their speaking rate and rhythm. If possible, these new findings will be incorporated into development of the spectral enhancement algorithm for clinical application. Finally, behavioral studies using a nonhuman mammal (chinchilla) will be conducted in order to establish a nonhuman model of auditory perceptual constancy that can be used in efforts to better understand the underlying physiology of spectral and temporal processing of complex sounds. [unreadable] [unreadable]